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CVE-2026-42236— n8n: Unauthenticated Denial of Service via MCP Client Registration

Quick assessment

Affected
n8n-io n8n
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

n8n是n8n开源的一个可扩展的工作流自动化工具。 n8n 1.123.32之前版本、2.17.4之前版本和2.18.1之前版本存在安全漏洞，该漏洞源于MCP OAuth客户端注册端点接受未经身份验证的请求且未对客户端数据进行充分资源控制，可能导致未经身份验证的远程攻击者通过发送大型注册有效载荷耗尽服务器内存资源，导致n8n实例不可用。

AI Predicted 7.5 Difficulty: Trivial EPSS 0.65% · P49

Affected Version Matrix 3

VendorProduct Version RangeStatus
n8n-io n8n < 1.123.32 affected
>= 2.17.0, < 2.17.4 affected
>= 2.18.0, < 2.18.1 affected
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I. Basic Information for CVE-2026-42236

Vulnerability Information
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Vulnerability Title
n8n: Unauthenticated Denial of Service via MCP Client Registration
Source: CVE Program / CVE List V5
Vulnerability Description
n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, the MCP OAuth client registration endpoint accepted unauthenticated requests and stored client data without adequate resource controls. An unauthenticated remote attacker could exhaust server memory resources by sending large registration payloads, rendering the n8n instance unavailable. The MCP enable/disable toggle gates MCP access but did not restrict client registrations, meaning the endpoint is reachable regardless of whether MCP access is enabled on the instance. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
n8n 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
n8n是n8n开源的一个可扩展的工作流自动化工具。 n8n 1.123.32之前版本、2.17.4之前版本和2.18.1之前版本存在安全漏洞，该漏洞源于MCP OAuth客户端注册端点接受未经身份验证的请求且未对客户端数据进行充分资源控制，可能导致未经身份验证的远程攻击者通过发送大型注册有效载荷耗尽服务器内存资源，导致n8n实例不可用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
n8n-io n8n < 1.123.32 -

II. Public POCs for CVE-2026-42236

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III. Intelligence Information for CVE-2026-42236

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Vendor Advisories for CVE-2026-42236 (1)

Same Patch Batch · n8n-io · 2026-05-04 · 12 CVEs total

CVE-2026-42232 n8n: XML Node Prototype Pollution to RCE
CVE-2026-42233 n8n: SQL Injection in Oracle Database Node via Limit Field
CVE-2026-42229 n8n: SQL Injection in SeaTable Node
CVE-2026-42228 n8n: Hijacking of Unauthenticated Chat Execution
CVE-2026-42235 n8n: XSS via MCP OAuth client
CVE-2026-42237 n8n: SQL Injection in Snowflake and MySQL Nodes
CVE-2026-42226 n8n: Credential Authorization Bypass in dynamic-node-parameters Allows Foreign API Key Rep
CVE-2026-42230 n8n: Open Redirect in MCP OAuth Consent Flow
CVE-2026-42234 n8n: Python Task Runner Sandbox Escape
CVE-2026-42227 n8n: Public API Variables IDOR Allows Cross-Project Secret Disclosure
CVE-2026-42231 n8n: Prototype Pollution in XML Webhook Body Parser Leads to RCE

IV. Related Vulnerabilities

Same product: n8n
Same vendor: n8n-io
Same weakness: CWE-770

V. Comments for CVE-2026-42236

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